Convergent-divergent variable area propulsion nozzle



Nov. 3, 1959 R. E. MEYER ETAL CONVERGENT-DIVERGENT VARIABLE AREA PROPULSION NOZZLE Filed Aug. 24. 1956 6 Sheets-Sheet l E- i K- BY ATTORNEY lu.. HH.- IBI Nov. 3, 1959 R. E. MEYER ET AL 2,910,828

CONVERGENTDIVERGENT VARIABLE AREA PROPULSION NOZZLE Filed Aug. 24, 1956 6 Sheets-SheetV 2 230 sa? 2E@ 265 62 1N\/ENTORS Z7@ ROBERT E. MEYER HIEMER K- NOREN 264 EVM ATTORNEY Nov. 3, 1959 R. E. MEYER ETAL coNvERGENT-DIVERGENT VARIABLE AREA PRoPULsIoN NozzLE Filed Aug. 24. 195e e sneetfsheet :s

INVEITOFQS ROBERT MEYER HILMER K.. NOREN ATTORNEY Nov. 3, 1959 R. E. MEYER ETAL 2,910,828

h CONVERGENT-DIVERGENT VARIABLE AREA PROPULSION NOZZLE Filed Aug. 24, 1956 6 Sheets-Sheet 4 IN VENTORS ROBERT E- MEYER H IL MEF? K- NOREQN Evy/WW1,

ATTOR NEY coNvERGENT--DIVERGENT VARIABLE AREA PRoPULsIoN NozzLE Filed Aug. 24, 195e Nov. 3, 1959 R. E. MEYER ETAL 6 Sheets-Sheet 5 FIG.V 2O

INVENTORS ROBERT E- MEYER HILMER K- NOREN EVM ,Y/mw

Nov. 3, 1959 R. E. MEYER ETAL 2,910,828

CONVERGENT-DIVERGENT VARIABLE AREA PROPULSION NOZZLE Filed Aug. 24, 1956 6 Sheets-Sheet 6 INVENTORS ROBERT E- MEYER HILMER K.. NOREN ATTORNEY United States Patent CONVERGENT-DIVERGENT VARIABLE AREA PROPULSION NOZZLE Robert E. Meyer, Glastonbury, and Hilmer K. Noren,

Manchester, Conn., assgnors to United Aircraft Company, East Hartford, Conn., a corporation of Delaware Application August 24, 1956, Serial No. `606,034

26 Claims. (Cl. 60-35.6)

This invention relates to exhaust nozzles for use on engines such as aircraft turbo-jet engines and, more particularly, to variable area exhaust nozzles.

it is an object of this invention to provide an exhaust nozzle which may be positioned in an infinite number of intermediate positions between its full open and full closed positions.

It is a further object vof this invention to provide a variable area exhaust nozzle which is convergent-divergent in all positions between full open and full closed.

lt is a further object of this invention to provide an exhaust nozzle which is actuated by a cam or wedge in combination with an opposed yoke unit.

it is a further `object of this invention to provide an exhaust nozzle which has a plurality of outer flaps and `a plurality of inner flaps, both of which 4may be uid or air cooled.

lt is a further object of this invention to provide an exhaust nozzle in which the gas loads imposed upon the exhaust nozzle flaps are taken in hoop tension by the flap actuating means.

it is a further object of this invention to provide a variable area convergent-divergent exhaust nozzle in which the nozzle throat area, the divergent nozzle angle, and the divergent nozzle length may be varied.

lt is still a further object of this invention to provide an exhaust nozzle with good base drag characteristics.

lt is Istill a furtherobject of this invention to provide an exhaust nozzle in which most of the ap actuating mechanism is completely enveloped within a doublewalled flap which forms an elongated annulus.

It is still a further object of this invention to provide an exhaust nozzle which has a plurality of outer flaps and a plurality of inner aps and in which one set of flaps is actuated by a cam and opposed yoke unit while the other set of flaps is actuated by the tirst set of flaps so actuated.

In the drawings:

Fig. 1 is a cross-sectional view of a typical aircraft turbo-jet engine with afterburner and with the double flap, variable area exhaust nozzle of the type to which this application relates attached to the afterburner.

Fig. 2 is a partial rear view of the double flap exhaust nozzle attached to an afterburner.

Fig. 3 is an enlarged view along line 3 3 of Fig. 2.

Fig. 4 is an enlarged view along line 4 4 of Fig. 2.

Fig. 5 is a view along line 5 5 of Fig. 4.

Fig. 6 is a view along line 6 6 of Fig. 5.

Fig. 7 is a view along line 7 7 of Fig. 3.

Fig. 8 is a side view of a portion of the interflap sealing means.

Fig. 9 is atop view of the interflap sealing means shown in Fig. 8. 1

Fig. 10 is a side view of another portion of the inter- `flap sealing means.

Fig. 11 is a top view of the `sealing means shown in Fig. 10.

Fig. 12 is a view taken along line 12 12 of Fig. 4.

Fig. 13 is a cross-sectional view of the inner flap interflap sealing means with the sealing surfaces abutting to show the exhaust nozzle closed position.

Fig. 14 is a cross-sectional view of an inner Hap showing a pin retaining means.

Fig. 15 is a bottom view of the structure shown in Fig. 14.

Fig. 16 is a view taken along line 16 16 of Fig. 14.

Fig. 17 is a cross-sectional view of an inner Hap show ing a second pin retaining means.

Fig. 18 is a View taken along line 18 18 of Fig. 17.

Fig. 19 is a partial bottom view of a configuration shown in Fig. 17.

Fig. 20 is a cross-sectional view of an inner ap showing still another type of pin retaining means.

Fig. 21 is a bottom view of the structure shown in Fig. 20.

Fig. 22 is a partial cross-sectional view of a single flap exhaust nozzle utilizing the cam and opposed yoke actuating mechanism.

Fig. 23 is a perspective showing of sealing strip to vane attaching lug.

Fig. 24 is a view taken along line 24 24 of Fig. 4.

Referring to Fig. l, we see aircraft turbo-jet engine 1l] comprising air inlet section 12, compressor section 14, combustion section 16, turbine section 18, afterburner section 20 and exhaust nozzle 2.2. Air enters air inlet section i2 and is compressed as it passes through compressor section 14 then is heated by combustion chambers 24 as it passes through combustion section 16. Fuel enters combustion chamber 24 through fuel nozzles 26 which are provided fuel by fuel manifold 28. Spark plug 3ft or other ignition means may be used to ignite the atomized fuel which enters combustion chamber 24. After leaving combustion section 16, the heated gases pass through turbine section 18 and thence through afterburner 20. In afterburner section Ztl, fuel is introduced through fuel spray bar 32 and is ignited by spark plug or other ignition means 34 while ameholders 36 are provided so that combustion may be supported downstream thereof.` After passing through and being reheated in afterburner section 20, the exhaust gases then pass through exhaust nozzle 22 and are discharged into the atmosphere so as to produce thrust. Exhaust nozzle 22 consists basically of a plurality of outer aps 40 and a pluralityv of inner flaps 42 which are surrounded by outer flaps 40. Exhaust nozzle 22 is shown in somewhat greater detail in Fig. 3 which shows afterburner cooling liner 44 located within and concentric with afterburner duct 46. Engine nacelle or other duct 48 is located outboard of and concentric with afterburner duct 46 and afterburner cooling liner 44 such that cooling air passage 50 is formed between afterburner cooling liner 44 and afterburner duct 46 while cooling air passage 52 is formed between afterburner duct 46 and engine nacelle or other duct 4S. The cooling air which passes through cooling air passages 50 and 52 may be provided from any convenient source, such as ram air, engine compressor air, or any bleed air from a relatively cool section of the engine. The cooling air or other fluid which passes through cooling passage 50 is discharged and ilowsV over the inner surface 54 of inner flaps 42 of exhaust nozzle 22. The cooling air or other iluid which passes through the cooling fluid passage 52 passes between outer flaps 40 and inner flaps 42 so as to cool the inner surface 56 of outer flaps 40 and the outer surface 58 of inner flaps 42. Still referring to Fig. 3, we see that afterburner duct 46 terminates in exhaust outlet 60, through which the gases from engine 10 are discharged after passing through afterburner 20. Afterburner duct 46 carries ring or attachment means 62 which permits inner tlaps 42 to be pivotally attached to exhaust outlet 60. Referring to Figs. 2 and 3, it will be noted that the plurality of inner flaps 42 are located circumferentially about and pivotally attached to exhaust outlet 60. Separating means 64 may be used to concentrically locate afterburner cooling liner 44 with respect to afterburner duct 46. Separating means 64 may consist either of a convoluted strip or a series of finger springs located circumferentially about afterburner duct 46 or may consist of a ring with a plurality of windows spaced circumferentially about the ring. Again referring to Fig. 3, it will be seen that projection or conical support member 66 extends outwardly from afterburner duct 46 and carries support ring 68. The plurality of outer aps 40 is pivotally attached to projection 66 through ring 68 and at pivot point 69. The plurality of outer aps 40 are located circumferentially about projection or conical support member 66 and, as best shown in Fig. 2, are separated such that spaces exist between adjacent outer aps 40.

Now referring to Figs. 3 and 4, we see that outer flaps 40 consist of inner wall 70 and substantially straight outer wall 72 spaced therefrom and a smooth fairing 74 smoothly connecting the after ends of inner wall 7G and outer wall 72. While not necessarily so limited, smooth faring 74 may be of substantially semi-circular crosssection. Inner wall 70 converges toward outer wall 72 at its after or downstream end 75 such that outer flaps 40, in combination with outer ap interflap sealing means 76, to be described later and shown in Fig. 2, wholly or partially form the divergent section of a convergentdivergent type exhaust nozzle throughout the full variable nozzle area range. inner wall 70 diverges away from outer wall 72 at its midlength section 73. It will be noted that connecting means or links 80 are pivotally attached to both outer flaps 40 at socket 81 and inner flaps 42 at hole 83 in web S5 (see Figs. 2 and 7), thereby connecting outer aps 40 with inner flaps 42, which are positioned within outer flap mdlength portion 73, such that thek actuation of either plurality of aps will actuate the outer plurality of flaps. Fig. 3 shows the plurality of inner flaps 42 and the plurality of outer flaps 40 in their extended position in solid lines and further shows both pluralities of flaps in their innermost position in phantom. It will be noted, as shown in Fig. 22, that outer aps 40 may be used without inner flaps 42 by pivotally attaching the outer aps 40" to exhaust outlet 60.

By referring to Figs. 2 and 4, we see that the plurality of outer flaps 40, are connected circumferentially by outer flap interflap sealing means 76, which permits relative circumferential movement between outer aps 40 and provides an exhaust nozzle with smooth inner and outer walls which are smoothly connected at their after ends lso as to wholly or partially form the divergent section of the exhaust nozzle. It will further be seen that inner flaps 42 have smooth inner surface 54 which is shaped convex inwardly when viewed from the centerline of powerplant 10 or concave inwardly when viewed from outer flaps 40 such that when in their extended position the plurality of inner aps 42, when combined with inner flap interflap sealing strips 82, form a smooth convergentdivergent nozzle which blends with the divergent exhaust nozzle formed by outer aps 40. When in their inner position as shown in phantom in Fig. 3, the plurality of inner flaps 42 form a convergent exhaust nozzle with outer flaps 40 so positioned with respect to inner flaps 42 that, in combination with fluid ow in annular passage 52, a divergent nozzle section is formed at all nozzle positions. Fluid ow in passage 52 which is exhausted through the annular orice formedby the after end of inner aps 42 and inner surface 56 of outer flaps 40 has the effect, in addition to the structure cooling efrect previously mentioned, of aerodynamically filling in the step between the inner flaps 42 and outer flaps 40 thus formling a smooth divergent shape ow path for the exhaust gases. It will further be noted that the inner flap interilap 4 sealing means of strip 82 (see Figs. 4 and 7) smoothly joins and attaches to inner aps 42 such that relative circumferential motion is permitted between inner aps 42 and sealing strip 82.

In the double flap configuration shown in Figs. 2, 3, and 4, the outer flaps 40 only are caused to actuate and since they are connected by connecting means 80, the actuation of outer flaps 40 also actuates inner aps 42. In the single flap configuration shown in Fig. 22, the same actuating means which is now to be described is used. This system consists of cam (Fig. 5) which is located circumferentially between adjacent outer flaps 40 and contained within outer Hap interflap sealing means 76 such that it is completely enclosed withinouter flaps 40 and sealing means 76. Cam 90 may have lightning holes 92 therein and carries roller unit 94 at its downstream or after end. Roller unit 94 may consist of bracket 96 which is attached to the after or downstream end of cam 90 by any convenient attachment means such as rivets 98 and further consists of ear-like projections 100 and 101 which carry rollers 104 and 102 in rotatable fashion and rollers 102 and 104 rotate about any convenient axis such as nut and bolt unit 106. Roller unit 94 also has track 108 which engages inwardly directed lip of outer ap interap sealing means 76 so as to position said sealing means and center it with respect to adjacent outer aps. It will be noted by referring to Fig. 5 that cam 90 has its greatest thickness at its after or downstreaml end and further has smooth side surfaces 112 and 114 against which the rollers of opposed yoke unit 116 bear and roll. Cam 90 is positioned so as to be substantially parallel to at least one of the plurality of ilaps 40 or parallel to adjacent outer aps 40. Roller unit 118 supports cam 90 at its forward or upstream end as the rollers 120 and 122 of roller unit 118 bear against or ride on tracks such as track 124. Any convenient axle such as nut and bolt unit 126 may be provided to permit the rolling of rollers 120 and 122. Variable length linkage 128 attaches the plurality of cams 90 which are positioned between adjacent outer aps 40 to actuating ring 130, while variable length linkage 132 attaches actuating ring 130 to a plurality of actuating cylinder and piston units, 134. Actuating cylinder and piston unit 134 consists of a piston within a cylinder, which piston is connected to linkage 132 and which is positioned within the cylinder by some uid force which is governed by a variable area exhaust nozzle control such as is described in co-pending U.S. application Serial No. 503,133, so as to cause actuating ring 130 to be positionable and to move fore and aft between its after position, as shown in solid lines in Fig. 4 and its forward position as shown in phantom in Fig. 4. When actuating ring 130 is in its after or downstream position, outer flaps 40 and inner flaps 42 are actuated to their outer position as shown in solid lines in Figs. 3 and 4 while when actuating ring 130 is in its farthest forward or upstream position as shown in phantom in Fig. 4, both inner aps 42 and outer flaps 40 are in their inner position as shown in phantom in Fig. 3. When actuating cylinder and piston unit 134 are governed by a variable area exhaust nozzle control as Vdescribed in the above-mentioned co-pending application,

actuating ring 130 and therefore flaps 40 and 42 may b e positioned in any intermediate position between their vinner and outer positions.

Fig. 3 shows track unit 136 which is a support for actuating ring 130 to insure that it is centrally located with respect to afterburner duct 46 and outer flaps 40. A plurality of track units such as 136 are attached to the forward inner surfaces of outer aps 40 and substantially equally spaced circumferentially about the exhaust nozzle formed by flaps 40. Track unit 136 may be placed on each flap 40 or may be placed in equally circumferential spaced relation but not on each flap 40. Track unit 136 projects inwardly and outwardly as it is carried by rotatr ing flap 40 and is so contoured that roller unit 138, which rl l is :attached to actuating ring 130, bears against the contoured track surface 140 of track unit 136.

Cam 90 may be any desired cam proportion so that the flaps of the exhaust nozzle operate at optimum speeds :and form optimum areas for the given power plant configuration instead of separating or operating uniformly. While not necessarily so limited, cam 90, as shown in Fig. 5, is in the shape of a simple wedge.

Referring to Figs. 3, and 6, we see that rollers 102 and 104 of roller unit 94 are located at the after end of cam 90 and engage tracks 150 and 152 of adjacent outer aps 40. Dimples or ribs 154 may be placed in tracks 150 and 152 to perform a strengthening function. As shown in Fig. 5, adjacent flaps 40 and 40 carry tracks 150 and 152, respectively, and these flaps engage rollers 102 and 104 of roller unit 94, respectively. It will be noted that tracks 150 and 152 are of considerably greater thickness at their after or downstream ends than they are at their forward ends and that the thickness of tracks 150 and 152 is uniformly progressive from `their front or forward ends to their after of downstream ends. Due to the increased thickness of tracks 150 and 152 at their downstream ends, the rearward or downstream movement of wedge `9) and roller unit `94 will cause adjacent outer flaps 40 and 40 to separate and thereby cause outer aps 40 to pivot or rotate outwardly to their outer position as shown in solid lines in Figs. 3 and 4. As flaps 40 separate and move toward their outer position, outer ap interflap sealing means 76 continue to center on projections 108 of roller unit`94 yet remain in frictional engagement with adjacent flaps 40 to form therewith a smooth surfaced exhaust nozzle of greater diameter. In practice, roller unit 94 will be assisted in moving exhaust nozzle 22 to its open position by the gas loading on the inner surface 56 of outer flaps 40 and the inner surface 54 of inner llaps 42. This gas loading imposes a force upon both flaps 40 and 42 so as to cause them to rotate or pivot outwardly to their outer or exhaust nozzle open positions.

Opposed yoke unit 116 yco-acts with cam 90 to cause aps 40 and 42 to rotate or pivot to or toward their inner or exhaust nozzle closed positions. Opposed yoke unit 116 consists of yoke 161) and opposed yoke 162. Yoke 160 is Y-shaped and consists of stem 164 and arms 166 and 168 and carries rollers 170 and 172 at the ends of `arms 166 and 16S. Rollers 1713 and 172 are attached to yoke 160 by any convenient axle means such as nut and bolt units 174 and 176. Stern 164 of yoke 168 has a hole 178 located at its extremity and a bolt 179 passes therethrough to engage a lug 1S@ in the interior of outer ap 4G such that yoke 169 and opposed yoke unit 1161's atttached to` outer flap 48 at the extremity of the stem of its Yshaped yoke while rollers 170 and 172 are pivotally attached to` the extremities of arms 166 and 168 of yoke 166 and bea-r against the lanti-flap side or surface 114 of cam or wedge 9G.

Opposed yoke 162 is `also Y-shaped in cross-section and, as is shown in Fig. 5, the arms 182 and 184 of opposed yoke 162 and the arms 1,66 and 168 of yoke 160 are directed toward each other while stem 186 of opposed yoke 162 and stem 164 of yoke 169 are positioned substantially perpendicular to the axis of cam 90. Opposed yoke 162 has hole 188 located in the extremity of stem 186 such that a bolt 189 may be passed through hole 188 so as to engage a lug comparable to lug 180 in the interior of adjacent outer ap 40 while roller units 196 and 192 are carried by arms 182 and 184 of opposed yoke 162 in thesame fashion as described for yoke 168 such that Vrollers 190 and 192 bear against the anti-flap surface 112 of cam 90. By referring to Figs. 4 and 5, it will be noted that yokes 160 attach to alternate outer flaps 40 while counter yokes 162 attach to the remaining flaps and that both yokes 160 and counter yokes 162 of opposed yoke unit 116 are positioned and located at about the middle of the length of aps 40.

Opposed yoke unit 116 works in conjunction with cam to cause flaps 40 and 42 to pivot or rotate to ortoward their inner or exhaust nozzle closed positions. As actuating cylinder-piston unit 134 causes actuating ring 134i to move forward or upstream, cam or wedge 90 also moves forward or upstream and as the respective rollers of yokes 166 and 162 bear against `cam surfaces 112 and 1141, the rollers are caused to separate due to the increased cam thickness therebetween as cam 90 moves forward. As rollers 190 and 192 of opposed yoke 162 are caused to separate from rollers 170 and 172 of yoke 160 due to the increased thickness of cam 9i) therebetween, the stem extremities at holes 178 and 188 of yoke 160 and opposed yoke 162, respectively, are drawn toward each other. Since the yoke and opposed yoke 162 stems are attached to adjacent outer flaps 46, the forward movement of cam or wedge 90 causes adjacent outer flaps 40 to be drawn closer to each other thereby causing outer aps 48 to pivot or rotate inwardly to or toward their inner or exhaust nozzle closed positions.

As pointed out previously, yoke 160 and opposed yoke 162 are located and attached to outer aps 40 at substanltially midlength of outer flap 40. Opposed yoke units 116 and the middle portions lengthwise of outer flaps `therefore form a hoop encompassing flaps 40, which hoop is positioned midway along the length of flaps 40. The hoop so formed performs the principal structural function inasmuch as it receives the gas loads acting on the inner surfaces of flaps 40 and 42 in hoop tension and in substantially balanced fashion due to its mid-length position. VSince the gas being discharged through exhaust nozzle 22 is of elevated temperature and high pressure, the strengthening function performed by the hoop so formed is of definite structural advantage to the exhaust nozzle since it directly absorbs most of the gas loads and thus -serves to prevent the overloading of other exhaust nozzle components and engine parts which support `the exhaust nozzle or which are attached to exhaust nozzle actuating parts.

The actuating means consisting of cam 90 and opposed yoke unit 116 perform additionally to assist exhaust nozzle flaps 40 and 42 to maintain their positions against the force of the exhaust nozzle `gas loads which operate on the inner surfaces of these aps to cause them to rotate or pivot to or toward the exhaust nozzle open position..

By assisting the exhaust nozzle aps to maintain their position by. absorbing the gas loads, the actuating means performs the additional function of preventing the gas loads imposed upon the flaps from being transferred to :the other engine parts, some of which may be located in critical tempera-ture or pressure location..

Now referring to Figs. 4, 6, 8, 9, l0, 11, a more particular description of the interflap sealing means '76 which is used between outer flaps `40 will be given. Interllap sealing means 76 is composed basically of two pieces, namely outer strip 20d and inner strip 220. Outer strip 200 as shown in Fig. 6, is contained within outer flaps 40 and engages outer walls 72 and adjacent flaps 40 in friction engagement and in overlapping fashion and extends substantially the full length of outer aps 40 such that it performs a seating function between adjacent outer flaps 40 and permits reiative circumferential movement between the outer flaps. Outer strip 269 is shown in more particular detail in Figs. 8 and 9 and by referring to these views, we see that outer strip 200 consists of sheet metal strip 292 which is a tapered strip with its greatest width at its downstream end.

The upstream end 204 may be slipped under spring lingers or the like, on adjacent outer flaps 40 so as to retain the forward end of outer strip 200 against the undersurface of outer walls 72 of adjacent outer flaps 40. The downstream end of outer strip 200 curves smoothly downwardly as shown in Fig. 8. It will be noted that hole 268 is located at the after end of outer strip 200 and that boss 210 is attached to the inner surface of outer strip 200 so that inner-diameter threads 212 aline with hole 208. As will be described later, hole 208 and boss 210 `are provided to connect outer strip 220. Track 214, which may or may not be interrupted, runs longitudinally along and is attached by welding or some other convenient method to the underside of outer strip 200. Lip 110 of track unit 214 is received between two pronged projections 108 of roller unit 94 so as to circumferentially position and center outer strip 200 and therefore interap sealing means 76 between adjacent outer flaps 40.

Inner strip 220 of interflap sealing means 76 is located inboard or exterior of the inner wall 70 of outer flap 40 and overlaps same in friction engagement so as to perform a sealing function and permit relative circumferential motion between the inner surfaces 70 of outer aps 40. Inner strip 220 is shown in greater details in Figs. 10 and 1l. Inner strip 220 consists basically of a sheet metal section 222 which has a smooth bend 224 at its after end. Hole 226 passes through the after end 224 of outer strip 220 and aligns with hole 208 and boss 210 of outer strip 200 so as to receive a bolt 211 to connect outer strip 200 with inner strip 220 at their after ends. The forward end of inner strip 220 is caused to bear against the undersurfaces of inner wall 70 of outer aps 40 by tab units 228. Tab units 228, as best shown in Fig. l0, are of L-shaped cross section with the base of the L spaced from sheet metal strip 222 substantially the distance of the thickness of inner wall 70 such that inner wall 70 of outer flap 40 passes between and is engaged on opposite sides by surface 230 of strip 220 and surface 232 of tab unit 228. Stiffening web 229 is provided on the undersurface of inner strip 220 to perform a strengthening function.

As best shown in Fig. 24, strip 220 is circumferentially positioned and centered with respect to adjacent outer flaps 40 by connection to outer strip 200 at its after end and by guide 221 at its forward end. Guide 221 is pivotally attached to guide arms 223, while guide arms 223 are pivotally attached to inner walls 70 of adjacent outer flap 40. Guide 221 has a recess therein which receives rib 229 of strip 220, thereby performing the positioning and centering function referred to supra.

When assembled as described above, inner strip 220 and outer strip 200 combine to form outer ap interflap sealing means 76 which are supported by outer flaps 40 and which move radially therewith but not circumferentially therewith since they are retained in circumferential position by roller unit 94 and guide unit 221. Sealing means 76 and flaps 40 combine to form an exhaust nozzle consisting of two spaced walls 70 and 72 which 50 present smooth exterior surfaces and form an elongated annulus or an annular member of V-shaped cross section which has a smoothly faired after end 74 to present good base drag characteristics and further to fully enclose cams 90, track units 94, opposed yoke units 116, roller units 11S and substantially all portions of the ap actuating mechanism excepting actuating ring 130 and actuating piston cylinder unit 134.

It will be obvious that since outer strip 200 is contained within outer flaps 40 while inner strip 220 is external of adjacent outer flaps 40 and since the two are connected at their after ends, axial motion between sealing means 76 and aps 40 is prevented. Further, tab units 223 combine with the action of attaching boss 210 to prevent radial motion between sealing means 76 and outer aps 40. It should be borne in mind that interiiap sealing means 76 engages adjacent outer flaps 40 in sealing engagement yet in sufficiently light friction engagement that circumferential relative movement is permitted between the sealing means and adjacent flaps as well as between adjacent flaps.

Now referring to Figs. 7, 13, 16 and 18 we note that inner flap interflap sealing means 250 is used to seal .between adjacent inner flaps 42. Inner iiaps 42 taper rearwardly, that is, the downstream end is narrower than the upstream end, `as shown in Fig. 15 and extend longitudinally from exhaust outlet 60 about which they are circumferentially located in spaced relation and to which they are pivotally attached. Inner flaps 42 have smooth undersurfaces 54 which are shaped convex inwardly as shown in Figs. 14 and 17. Inner flap interap sealing strips 32, which is a part of sealing means 250, may be flat sheet metal plates which are forwardly tapering, that is, they have their greatest thickness at their after or downstream ends and form a longitudinally extending seal strip between and bearing juxtapositioned between and bearing against the undersurfaces 54 of adjacent inner flaps 42. Lug 252 extends upwardly from sealing strip 82 and has a longitudinally extending recess or slot 253 therein (see Fig. 23), which we will see later serves in part to secure sealing strip 82 to adjacent inner aps 42 and also serves to center sealing strip 82 with respect to circumferentially movable adjacent inner flaps 42.

It will be noted by referring to Figs. 20 and 2l that sealing strip 82 has tabs 254 at its after or downstream end which engage the trailing edges of adjacent inner aps 42 such that tabs 254 and lug 252 combine to attach sealing strip 82 to adjacent inner aps 42. Slot 253' engages pin 294 to hold seal 82 against flaps 42.

Since innerfiaps 42 are pivotally attached to and positioned circumferentially about exhaust outlet 60, and further, since sealing strips 82 smoothly connect adjacent inner flaps 42 such that relative circumferential movement is permited between adjacent aps 42 and since sealing strips 82 are carried by inner flaps 42, the plurality of inner flaps 42 and sealing strips 82, when assembled, as shown in Fig. 2, form a variable area exhaust nozzle through which the exhaust gases being discharged from engine l@ must pass.

As shown in Fig. 2l, inner ap 42 has troth-shaped retaining means 256 extending substantially the full length of the longitudinal edges of iiaps 42. Troth-shaped retaining means 256 carry longitudinal grooves 258 therein. The retaining track or projection formed by troth-shaped retaining means 256 is interrupted in its length as is longitudinal groove 258 therein, as is best shown in Fig. 2l.

While sealing strips 82 form a portion of inner ap interap sealing means 250, the second portion of this sealing means 250 is best shown in Figs. 7, 13, and 20. This portion of the inner flap interflap sealing means 250 comprises two tapered sheet metal pieces or ilat plates 260 and 262 which are pivotally attached to each other at their top surfaces either by forming concentric sheet metal rolls as at 264 in Figs. 7 and 13 or by each engag- Ming rolled sheet metal strip 266, as shown in Fig. 18. The bottom surfaces of tapered sheet metal pieces or at plates 260 and 262 are curled and pivotally engage the longitudinal grooves 25S in the retaining tracks 256 of adjacent inner ilaps 42 as shown in Figs. 7, 16, and 18. It will be noted that sheet metal pieces 260 and 262 are tapered uniformly throughout their length such that their greatest height exists at their downstream or after ends and that they are located external of and between adjacent inner flaps 42 and extend substantially the full flap length. Sheet metal pieces 26u and 262 have sealing or sheet metal surfaces 268 and 270 which abut one another juxtapositioned and in sealing relation to perform a sealing function between adjacent flaps 42 when the exhaust nozzle formed by flaps 42 is in its minimum area position. The exhaust nozzle is in its minimum area position when adjacent iiaps 42 are at their closest circumferential positionV with respect to each other. As the exhaust nozzle formed by inner iiaps 42 expands and flaps 42 separate, the sealing surfaces 268 and 270 of sheet metal strips 26@ and 262 separate as they pivot about each other at their top surfaces or ends 264 and as they pivot about the retaining tracks 256 of adjacent flaps 42 such that sheet metal pieces 26@ and 262 form a triangular sealing passage 272 with aps 42. This triangular passage formed by sheet metal pieces -260 and 262 and flaps *42 galones is maximum in area when the exhaust nozzle is in its maximum area position. Sheet metal pieces 260 and 262 are retained in proper axial position with respect to flaps 42 by any convenient means such as wire hook 274 which passes through interrupted groove 258 or interrupted track 256 as shown in 21 and is bent so as to prevent rearward movement of sealing pieces 260 and 262. As further shown in Fig. 21, pin or cotter pin 276 may be passed throughl lu g 278 which projects from sealing strip 282 such that pin 276 blocks the forward end' of retaining tracks 256 of adjacent flaps 42 to prevent forward axial movement of sealing pieces 260 and 262.

It will be noted as shown in Figs. 7 and 13 that the sheet metal pieces 260 and 252 have opposed circumferentially directed strips or steps 280 and 282 positioned internal of sealing surfaces 263 and 270. These opposed, circumferentially directed steps permit sealing surfaces 265 and 270 of sheet metal pieces 260 and 252, respectively to abut in sealing relation when inner llaps 42 are in their closest circumferential position when the exhaust nozzle formed by flaps 42 is in its minimum area position. Steps 2S@ and 282 perform the additional function of forming a very small and rearwardly directed gas leakage passage 22134;-, as shown in Fig. 13, with aps l2 through which any gas which may escape between sealing strip 82 and adjacent inner flaps e2 will be directed and discharged rearwardly in a thrust generating and thrust recovery function. That is, the thrust which is lost in the overall power plant output due to this gas leakage between adjacent inner llaps 42 is caused to pass through small passage 284 and be discharged rearwardly therethrough in a thrust generating functie-n so as to regain the thrust lost due to gas leakage.

For optimum thrust output it is highly desirable that the exhaust nozzle presented by the plurality of llaps forming the exhaust nozzle be of circular cross section. When a series of overlapping flaps (see Figs. 16 and 1S) or a series of flaps joined by interilap sealing means which overlap adjacent flaps (see Fig. 7) are used to form the exhaust nozzle, and the relative circumferential movement permitted between adjacent flaps is not limited, it is possible that certain ilaps will separate circumferentially from their adjacent aps to a greater extent than the remaining flaps such that either a non-circular exhaust outlet is presented or adjacent overlapping flaps separate such that the gas is discharged through a form other than a circle. To prevent this excessive circumferential relative motion between adjacent flaps and to thereby retain an exhaust nozzle of substantially circular cross-section, motion limiting pins of the type shown in Figs. 14, 17, 2O and 21 are used.

For purposes of illustration, three different types of motion limiting and centering pins 29d are shown. These pins are :located outboard of the exhaust nozzle flaps such as lla s 42 and 11m laterally between adjacent llaps 42 and are so positioned that projections 229 and 292, which are located at the ends of limiting pins 29d, project beyond adjacent tracks or projections 256 on adjacent flaps l2 and pass ythrough the interruptions of said tracks 256 such that pin projections 290 and 292 engage ap projections 256 to prevent adjacent flaps 42 from moving relative to each other beyond a pre-determined limit. The pin shown in Figs. 14, l5, and 16 is hat at cross-section as is best shown in Fig. 14, and has llat end projections 2% and 292 while the pin-shown in Figs. 17, 18 and 19 is substantially circular in cross-section and has projections 299 and 292 of circular cross-section at its ends. As shown in Figs. 16 and`l8, limiting ins 294 may be used to limit the relative circumferential movement between adjacent flaps 42 when such adjacent flaps form an exhaust nozzle by overlapping one another. Pin 294 is retained in position by sealing means 25u.

Now referring to Figs. 2O and 2l, we see that flaps ll2 are `of a variety which do not overlap one another but which are joined circumferentially by sealing strips 82. The centering pin 294, shown in Figs. 20 and 21, while not necessarily so limited, is flat in cross-section as are its end projections 290 and 292. In addition to these end projections, this pin 294 has substantially' center positioned, spaced projections Still and 362 which, when as- 'ernblech are ilocated on the opposite sides of lug 252 which projects trom sealing strip 82. The longitudinal groove 253 in lug 252 envelops section 3M of pin 222 which is located between central projections 300 and 302. Central projections Cibi) and 3F32, by engaging sealing strip lug 2a23 permit pin 2% to perform the additional function of centrally positioning overlapping sealing strip `82 between adjacent inner llaps d2. In short, the pin 294 shown in Figs. Z and 2l not only limits circumferential relative motion between adjacent flaps 42 but also centrally positions sealing strip 32 with respect `to adjacent flaps 42. Unit 25d retains pin 294.

Now referring to Fig. 3 We see the double flap exhaust nozzle 22 in its outer position in solid lines and in its inner position in phantom. When in its inner position, the minimum nozzle throat area is presented as is the minimum divergent length and angle (all as shown) between inner llaps 42 and outer flaps 4l0. When aps 42 and 40 are in their outer position, the maximum nozzle throat area and the maximum divergent angle and length between these flaps is presented. As exhaust nozzle 22 moves from its inner postion to its outer position, the throat nozzle area will increase as will the divergent angle and the divergent length of the exhaust nozzle.

It will be noted that in its inner position, flaps 42 form a convergent exhaust nozzle, while in their outer position, flaps 42 form a convergent-divergent exhaust nozzle, due to convex inner surface 54.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

We claim:

1. ln an exhaust nozzle of circular cross section and concentric about an axis, a plurality of circumferentially positioned daps having radially spaced inner and outer walls joined smoothly at their after ends to form an annular chamber, a cam member positioned within said annular chamber and substantially parallel to and located between adjacent flaps and movable with respect thereto, an opposed yoke unit positioned within said annular chamber and attached to each of said adjacent flaps at ilap midlength and bearing against opposite sides of said cam member such that the movement of said cam members causes the actuation of said llaps.

2. In an exhaust nozzle of circular cross section, a plurality of circumferentially positioned pivotable flaps, cam members positioned between adjacent flaps and longitudinally movable with respect thereto, a circumferentially extending Y-shaped yoke member attached to alternate flaps, a circumferentially extending Y-shaped opposed yoke member attached to the remaining llaps and extending in the opposite direction to said yoke members such that a yoke member and an opposed yoke member bear against opposite surfaces of each of said cam members to cause flap actuation as said cam members are moved with respect to said l'laps, each of said yoke members and said opposed yoke members being supported by engaging a cam member and a ilap solely and making contact therewith at points of equal radial dimension so that said cam members, yoke members, opposed yoke members and flaps form a circle to receive ilap gas loads in hoop tension with said yoke and opposed yoke members loaded in tension.

3. In an exhaust nozzle of circular cross section concentric about an axis, an exhaust duct, a plurality `of circumferentially positioned flaps pivotally attached to said exhaust duct, wedge shaped members having maximum thickness at their after end positioned between ad jacent flaps and axially movable with respect thereto, actuating means attached to said exhaust duct and said wedge shaped members to move said wedge shaped members and to restrain said wedge shaped members in xed position, a circumferentially extending Y- shaped yoke member attached at the stem of the Y- to alternate flaps at flap midlength, a circumferentially extending Y-shaped opposed yoke member attached at the stem of the Y to the remaining flaps at flap midlength, said yoke member and said opposed yoke member supporting a roller on each arm of the Y and extending in opposite directions such that the rollers of said yoke member and said opposed yoke member bear against opposite surfaces of one of said wedge shaped members to cause flap actuation as said wedge shaped members are moved with respect to said flaps and further such that said wedge shaped members, said yoke members, said opposed yoke members and said aps coact to form a circle to receive flap gas loads in hoop tension with said actuating means, said yoke members and said opposed yoke members loaded in tension and further such that one of said wedge shaped members and one of said flaps constitutes the sole support of each of said yoke members and each of said opposed yoke members.

y 4. In an exhaust nozzle, an exhaust outlet, a plurality of flaps located circumferentially about and pivotable with respect to said exhaust outlet, a track unit on the longitudinal edges of each of said ilaps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam members being positioned between adjacent flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps, an opposed yoke member attached to the remaining flaps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said flaps, and said cam member roller unit engaging said track units on adjacent flaps to cause `flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said flaps.

5. In an exhaust nozzle, an exhaust outlet, a plurality of flaps located circumferentially about and pivotable with respect to said exhaust outlet, a track unit on the longitudinal edges of each of said ilaps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent flaps and'moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate aps, an opposed yoke member attached to the remaining aps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause ap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect `to said laps, said cam member roller unit engaging said track units on adjacent flaps to cause flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said flaps, and means to actuate said cam members.

6. In an exhaust nozzle, an exhaust outlet, a plurality of aps located circumferentially about and pivotable .with respect to said exhaust outlet, a track unit on the longitudinal edges of each of said aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends,

said cam member being positioned between adjacent aps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate aps, an opposed yoke member attached to the remaining aps such that said yoke memf ber and said opposed yoke member bear against opposite surfaces of a cam member to cause ap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said aps, said cam member roller unit engaging said track units on adjacent aps to cause ap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said ilaps, a ring unit lying in a plane parallel to said exhaust outlet, means to at,- tach said ring to'said cam members, and means to actuate said ring in a forwardly or upstream and rearwardly or downstream direction.

7. In an exhaust nozzle, an exhaust outlet, a plurality of flaps with spaces therebetween located circumferentially about and pivotable with respect to said exhaust outlet, interflap sealing means located between adjacent aps, a track unit on the longitudinal edges of each of said aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps, an opposed yoke member attached to the remaining flaps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause lap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said flaps, said cam member roller unit engaging said track units on adjacent flaps to cause flap actuation toward an exhaust nozzle maximum area position as said cam members are rinoved rearwardly or downstream with respect to said aps.

8. In an exhaust nozzle, an exhaust outlet, a plurality of ilaps with spaces therebetween located circumferentially about said exhaust outlet and pivotable with respect thereto, interflap sealing means located between adjacent flaps and filling the spaces therebetween and engaging adjacent aps to permit relative circumferential movement therebetween, a track unit on the longitudinal edges of each of said flaps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps, an opposed yoke member attached to the remaining flaps, such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation towar and exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said aps, said cam member roller unit engaging said track units on adjacent flaps to cause flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said flaps.

9. In an exhaust nozzle, an exhaust outlet, a plurality of flaps located circumferentially about and pivotable with respect to said exhaust outlet, a track unit on the longitudinal edges of each of said aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent aps and movable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps and located at about the middle of the ap length, an opposed yoke member attached to the remaining aps and located at about the middle of the ap length such that said yokes and opposed yokes lie in a plane perpendicular to the exhaust nozzle centreline to form a hoop with the ap sections at mid-flap length to resist flap movement due to ap gas loading, said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said flaps, said cam member roller unit engaging said track units on adjacent flaps to cause ap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said flaps.

10. In an exhaust nozzle, an exhaust outlet, a plurality of aps with spaces therebetween located circumferentially about and pivotable with respect to said exhaustV outlet, said aps having a spaced inner and outer wall with a smooth fairing connecting said inner wall and said outer wall at their after ends, a track unit on the longitudinal edges of each of said flaps located between said inner wall and said outer wall of said dips, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps, an opposed yoke member attached to the remaining flaps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause ap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said flaps, said cam member roller unit engaging said track units on adjacent flaps to cause flap actuation toward an exhaust nozzle maximum-area position as said cam members are moved rearwardly or downstream with respect to said flaps, interap sealing means positioned between and smoothly connecting adjacent flaps such that said flaps and said interflap sealing means overlap permitting relative circumferential motion therebetween and further such that said aps and said interap sealing means form an elongated annulus having smooth exterior surfaces which annulus encloses said track units, said cam members, said yoke members, said opposed yoke members and said roller units.

1l. In an exhaust nozzle, an exhaust outlet, a plurality of flaps with spaces therebetween located circumferentially about and pivotable with respect to said exhaust outlet, said flaps having a spaced inner and outer wall with a smooth fairing connecting said inner wall and said outer wall at their after ends, the inner wall of said flap converging toward said outer wall at its after end, a track unit on the longitudinal edges of each of said flaps located between said inner wall and said outer wall of said flaps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said'cam members being positioned between adjacent aps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate flaps, an opposed yoke member attached to the remaining aps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said flaps, said cam member roller unit engaging said track units on adjacent tiaps to cause flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said flaps, interap sealing means positioned between and smoothly connecting adjacent tlaps such that said flaps and said interllap sealing means overlap permitting relative circumferential motion therebetween and further such that said aps and said interap sealing means form an annulus of a roughly V-shaped cross section having smooth exterior surfaces, and such that a divergent nozzle is formed by the after end `ot".said iiaps and said interilap sealing means, which annulus encloses said track units, said cam members, said yoke members, said opposed yoke members, and said roller units.

12. An aircraft jet engine having a compressor and a turbine, a combustion section between said compressor and turbine and further having an afterburner attached to said turbine, in combination with an exhaust nozzle located at the after end of said afterburner including an exhaust outlet,` a plurality of flaps with spaces therebetween located circumferentially about and pivotable with respect to said exhaust outlet, said aps having a spaced inner and outer wall with a smooth fairing connecting said inner wall and said outer wall at their after ends, a track unit on the longitudinal edges of each of said flaps located between said inner wall and said outer wall of said flaps, wedge members having their greatest thickness at their after ends and further having a roller unit at their after ends, means to support the forward end of said wedge member, said wedge member being positioned between adjacent flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached at one end to alternate flaps, an opposed yoke member attached at one end to the remaining iiaps, said yoke member and said opposed yoke member having roller units attached to their antiap ends such that said roller units of said yoke member and said opposed yoke member bear against surfaces of a wedge member opposite to the flap to which their respective yokes are attached to cause flap actuation to- Ward an exhaust nozzle minimum area position as said wedge members are moved forwardly or upstream with respect to said flaps, said wedge member roller unit engaging said track units on adjacent flaps to cause flap actuation toward an exhaust nozzle maximum area position as said wedge members are moved rearwardly or downstream with respect to said flaps, interflap sealing means positioned between and smoothly connecting adjacent aps such that said flaps and said interflap sealing means overlap permitting relative circumferential motion therebetween and further such that said flaps and said interiiap sealing means form an elongated annulus having smooth exterior surfaces which annulus encloses said track units, said wedge members, said yoke members, said opposed yoke members, and said roller units, and means to center said interilap sealing means with respect to their adjacent flaps.

13. Exhaust nozzle flap actuating means comprising a wedge shape member having its greatest thickness at its after end and positioned parallel to and `located between adjacent tiaps and movable with respect thereto, actuating means to so move said wedge shaped member and to restrain said wedge shaped member in iixed position, an opposed yoke unit comprising Y-shaped members engaging adjacent flaps and bearing against said wedge shaped member on a side opposite to its flap attachment such that the movement of said wedge shaped member actuates the ilaps and further such that said wedge shaped member and said opposed yoke unit coact to maintain flap position against gas loading with said opposed yoke unit and actuating means loaded in tension. Y

14. Exhaust nozzle flap actuating means comprising a cammember positioned parallel to and located between adjacent aps and moveable with respect thereto, an opposed yoke unit comprising two Y-shaped yokes positioned with the arms of each of said Y-shaped yokes directed toward each other while the stems or" each of said Y-shaped yokes a-re substantially perpendicular to the axis of said cam, the stems of said Y-shaped .yokes engaging 'adjacent flaps, roller units attached to the arms of each :unit comprising two Y-shaped yokes positioned with the .arms of each of said Y-shaped yokes directed toward each other while the stems of each of said Y-shaped yokes vare substantially perpendicular to the axis of said cam, the stems of said Y-shaped yokes engaging adjacent flaps, yroller units attached to the arms of each of said Y-shaped yokes, said roller units bearing against said wedge on a surface opposite to the ap to which each Y-shaped yoke is attached such that the movement of said wedge actuates the aps.

16. In a variable area, convergent-divergent exhaust -nozzle having an axis, a plurality of pivotal and axially elongated outer flaps, a cam member positioned substantially parallel to adjacent outer ilaps and movable with respect thereto, a yoke member attached to each adjacent outer ap and bearing against said cam member such that the movement of said cam member causes the pivotal actuation of said adjacent outer ilaps, and a plurality of pivotal inner flaps having smooth inner surfaces which are shaped convex inwardly and attached to said outer flaps so that the actuation of said outer flaps actuates said inner aps, said inner aps being of substantially shorter axial dimension than, located radially inboard of, terminating substantially axially forward of said outer flaps and having a contour so that said inner aps form the convergent and throat portions and coact with said outer laps to form the divergent portion of a convergent-divergent exhaust nozzle for all ap portions.-

l7. In a variable area, convergent-divergent exhaust nozzle of ci-rcular cross section and having an axis, a plurality of circumferentially positioned, pivotal and axially elongated outer flaps, said outer flaps having an elongated and substantially straight outer wall and further having an inner wall spaced inwardly from said outer wall, said inner wall being substantially parallel to said outer wall at its forward end then dive-rging away from said outer wall at substantially its midlength section and then converging toward said outer wall at its after end, a carn member positioned substantially parallel to and located between adjacent outer flaps and movable longitudinally with respect thereto, an opposed yoke unit attached to each of said adjacent outer aps and bearing against opposite sides of said cam member such that Vthe movement of said cam members causes the pivotal actuation of said outer aps, and a plurality of pivotal inner ilaps located inboard of said outer flaps approximately within said outer flap midlength section and at- Vtached to said outer iiaps so that the actuation of said outer Flaps actuates said inner llaps, said inner flaps being of substantially shorter axial dimension than, terminating substantially axially forward of said outer aps and having a contour so that said inner aps form the convergent and throat portions and coact with said outer apsto form the divergent portion of a convergent-divel-gent exhaust nozzle for all flap positions which exhaust nozzle is of minimum throat area, divergent angle and divergent length when said flaps are in their innermost pivot position and which exhaust nozzle is of maximum throat area, divergent angle and divergent length when said ilaps are in their outermost pivot position.

18. in an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer rflaps located eircumferentially about and pivotable with respect to said projection, a track unit on the longitudinal edges of each of said outer aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam members being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer flaps, an opposed yoke member attached to the remaining outer tlaps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with -respect to said outer aps, and said cam member roller unit engaging said track units on adjacent outer aps to cause ap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said outer aps, a plurality of inner flaps located circumferentially about and pivotable with respect to said exhaust outlet, and means to connect said inner ilaps to said outer flaps such that the actuation of said outer flaps actuates said inner aps.

19. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer aps located circumferentially about and pivotable with respect to said projection, a track unit on the longitudinal edges of each of said outer aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam members being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer flaps, an opposed yoke member attached to the remaining outer aps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said outer flaps, said cam member roller unit engaging said track units on adjacent outer flaps to cause Hap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said outer aps, means to actuate said cam members, a plurality of inner aps located circumferentially about and pivotable with respect to said exhaust outlet, and means to connect said inner flaps to said outer ilaps such that the actuation of said outer aps actuates said inner flaps.

20. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer llaps located circumferentially about and pivotable with respect to said projection, a track unit on the longitudinal edges of each of said outer flaps, earn members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer aps, an opposed yoke member attached to the remaining outer flaps such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause ap actuation toward an exhaust nozzle minimum area position as saidA cam members are ,moved forwardly or upstream with respect to said outer aps, said cam member roller unit engaging said trackunits on adjacent outer aps to cause Hap actuationtoward an exhaust nozzle minimum area position. as said cam members are moved rearwardly or downstream with respect to said outer flaps, a ring unit lying in a plane parallel to said exhaust outlet, means to attach said ring to said can members, means to actuate said ring in a forwardly 17 or upstream and rearwardly or downstream direction, a plurality of inner flaps located circumferentially about and pivotable with respect to said exhaust outlet, and means to connect said inner flaps to said outer aps such that the actuation of said outer flaps actuates said inner flaps.

21. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer flaps with spaces therebetween located circumferentially about and pivotable with respect to said projection,` intertlap sealing means located between adjacent outer ilaps, a track unit on the longitudinal edges of each of said outer llaps,` cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent outer aps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer flaps, an opposed yoke member attached to the remaining outer flaps, such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause iiap actuation toward an` exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with Irespect to said outer ilaps, said cam member roller unit engaging said track units on adjacent outer flaps to cause ilap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said ilaps, a plurality of inner aps located circumferentially about and pivotable with respect to said exhaust outlet, and means to connect said inner ilaps to said outer flaps such that the actuation of said outer flaps actuates said inner aps.

22. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer aps with spaces therebetween located circumferentially about said projection and pivotable with respect thereto, interflap sealing means located between adjacent outer flaps and lling the spaces therebetween and engaging adjacent outer ilaps to permit relative circumferential movement therebetween, a track unit on the longitudinal edges of each of said outer flaps, cam mem- 'bers having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer ilaps, an opposed yoke member attached t the remaining outer aps, such that said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said outer liaps, said cam member roller unit engaging said track units `on adjacent ilaps to cause iiap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said outer flaps, a plurality of inner flaps located circumferentially about and pivotable with respect to said exhaust outlet, and means to connect said inner tlaps to said outer flaps such that the actuation of `said outer aps actuates said inner flaps.

23. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer flaps located circumferentially about and pivotable with respect to said projection, a track unit on the longitudinal edges of each of said outer aps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer flaps V18 and located at about the middle of the ap length, an opposed yoke member attached to the remaining outer flaps and located at about the middle of the ilap length such that said yokes and opposed yokes line in a plane perpendicular to the exhaust nozzle centerline to form a hoop with the iiap sections at mid-Hap length to resist tlap movement due to ilap gas loading, said yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause ap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said outer flaps, said cam member roller unit engaging said track units on adjacent outer flaps to causeV flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with` respect to said outer flaps, a plurality of inner aps located circumferentially about and pivotable with respectto said exhaust outlet, and means to connect said inner aps to said outer aps such that the actuation of said outer flaps actuates said inner aps.

24. In an exhaust nozzle, an` exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer i'laps with spaces therebetween located circumferentially about and pivotally attached to said projection, said outer flaps having a spaced inner and outer wallA with a smooth fair-ing connecting said inner wall and said outer wall at their after ends, a track unit on the longitudinal edges of each of said outer aps located between said inner wall and said outer wall of said outer iiaps, cam members having their greatest thickness at their downstream ends and further having a roller unit at their downstream ends, said cam member being positioned between adjacent outer llaps and moveable forwardly or upstream and rearwardly or downstream with respect thereto, a yoke member attached to alternate outer tlaps, an opposed yoke member attached to the remaining outer flaps such that said yoke member and said opposed yoke member 'bear against opposite surfaces of a cam member to cause flap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said outer flaps, said cam member roller unit engaging said track units on adjacent outer tlaps to cause iiap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly or downstream with respect to said outer ilaps, interflap sealing means positioned between and smoothly connecting adjacent outer flaps such that said outer flaps and said outer flap interilap sealing means overlapV permitting relative circumferential motion therebetween and further such that said outer flaps and said outer flap interap sealing means form an elongated annulus having smooth exterior surfaces which annulus encloses said track units, said cam members, said yoke members, said opposed yoke members and said roller units, a plurality of inner flaps located circumferentially about and pivotally attached to said exhaust outlet, said inner flaps having smooth inner surfaces which are concave inwardly in shape such that said inner flaps form a convergent-divergent passage, and means to connect said inner flaps to said outer aps such that the actuation of said outer flaps actuates said inner flaps.

25. In an exhaust nozzle, an exhaust outlet, a projection extending outwardly from said exhaust outlet, a plurality of outer ilaps with spaces therebetween located vcircumferentially about and pivotally attached to said projection, said outer flaps having a spaced inner and outer wall with a smooth fairing connecting said inner wall and said outer wall at their after ends, the inner wall of said iiap converging toward said outer wall at its after end, a track unit on the longitudinal edges of each `of said outer ilaps located between said inner wall and said outer wall of said outer i'laps, cam members having their greatest thickness at their downstream ends, said cam member being positioned between adjacent 19 outer flaps and moveable forwardly or upstream and rear wardly or downstream with respect thereto, a yoke member attached to alternate outer flaps, an opposed yoke member and said opposed yoke member bear against opposite surfaces of a cam member to cause ilap actuation toward an exhaust nozzle minimum area position as said cam members are moved forwardly or upstream with respect to said outer flaps, said cam member roller unit engaging said track units on adjacent outer flaps to cause flap actuation toward an exhaust nozzle maximum area position as said cam members are moved rearwardly orV downstream with respect to said aps, interlap sealing means positioned between and smoothly connecting adjacent outer flaps such that said outer flaps and said outer flap interap sealing means overlap permitting relative circumferential motion therebetween and further such that said outer flaps and said outer flap interiiap sealing means form an annulus of a roughly V-shaped cross section having smooth exterior surfaces, and such that a divergent nozzle is formed by the after end of said outer flaps and said outer flap interflap sealing means, which annulus encloses said track units, said cam members, said yoke members, said opposed yoke members, and said roller units, a plurality of inner flaps located circumferentially around and pivotally attached to said exhaust outlet, interilap scaling means smoothly joining `adjacent inner flaps to permit circumferential relative movement therebetween, said inner flaps having smooth inner surfaces which are concave inwardly in shape with respect to exhaust nozzle centerline such that said inner iiaps form a convergent exhaust nozzle when said ilaps are in their inner position and such that said inner flaps and said inner and outer flaps form a convergent-divergent exhaust nozzle when said aps are in their outer position and further such that said inner flaps and said outer flaps form a convergent-divergent exhaust nozzle of varying divergent angle and length when said inner aps and said outer ilaps are in intermediate positions, and means to Vconnect said inner aps to said outer iiaps such that the actuation of said outer aps actuates said inner flaps.

26. An aircraft jet engine having a compressor and a turbine, a combustion section between said compressor Vand turbine and further having an afterburner attached to said turbine, iu combination with an exhaust nozzle located at the after end of said afterburner including an exhaust outlet, a projection extending outwardly from said exhaust nozzle, a plurality of outer flaps with spaces therebetween located circumferentially about and pivotally attached to said projection, said outer aps having a V20 spaced inner and outer wall with a smooth fairintg connecting said inner wall and said outer wall at their after ends, a track unit on the longitudinal edges of each of said outer flaps located between said inner wall and said outer wall of said outer flaps, wedge members having their greatest thickness at their after ends and further having a roller unit at their after ends, means to support the forward end of said wedge member, said wedge member being positioned between adjacent outer flaps and moveable forwardly or upstream and rearwardly or downstream With respect thereto, a yoke member attached at one end to alternate outer flaps, an opposed yoke member attached at one end to the remaining outer flaps, said yoke member and said opposed yoke member having roller units attached to their antiap ends such that said roller units of said yoke member and said opposed yoke member bear against surfaces of a wedge member opposite to the ap to which their respective yokes are at tached to cause flap actuation toward an exhaust nozzle minimum area position as said wedge members are moved forwardly or upstream with respect to said outer aps, said wedge member roller unit engaging said track units on adjacent outer aps to cause flap actuation toward an exhaust nozzle maximum area position as said wedge members are moved rearwardly or downstream with respect to said outer iiaps, interlap sealing means positioned between and smoothly connecting adjacent outer flaps such that said aps and said outer flap interap `sealing means overlap permitting relative circumferential motion therebetween and further such that said outer flaps and said outer flap interilap sealing means form an elongated annulus having smooth exterior surfaces which annulus encloses said track units, said wedge members, said yoke members, said opposed yoke members and said roller units, means to center said interflap sealing means with respect to their adjacent outer flaps, a plurality of inner flaps located circumferentially about and pivotally attached to said exhaust outlet, and means to connect said inner aps to said outer flaps such that the actuation of said outer flaps actuates said inner ilaps.

References Cited in the file of this patent UNITED STATES PATENTS 2,796,731 Morley et al Ian. 25, 1957 FOREIGN PATENTS 525,114 Belgium Jan. 15, 1954 742,875 Great Britain Jan. 4, 1956 UNITED STATES PATENT OFFICE CERTIFICATE or CORRECTION Patent No., zioze November 3 w59 v `Robert Eo Meyer et al lt is hereby certified that error appears in the printed specification of the above numbered patent' requiring Correction and that the said Letters Patent should read as Corrected belowa Column l2? lines 55 and 56Y ior actuation tower and exhaust" read actuation toward an exhaust --mg Column 13Y line 2lq ior "flips" read laps Column l5Y line 39Y for "portions" read positions Column lg line 7l for "minimum" rend` maximum -g Column lf3Y line Y ior linen read lie Signed end sealed this 5th day oi July l9Oo (SEAL) Attest:

KARL H., AXLINE ROBERT C. WATSON Attesting Officer Conmissioner of Patents 

